Known Hardware Info Edit
Most of the relevant GPIOs can be found on Handhelds.org's Axim X50 hardware page. Paul Nicholls is currently working on identifying the remaining GPIOs required to make a derivative of the Handhelds.org kernel's HX2750 PCMCIA driver work on the Axim.
Current Status Edit
Paul Nicholls is currently working on a driver based on the Handhelds.org kernel's HX2750 PCMCIA driver, as it appears to be virtually identical (except using different GPIOs). He has obtained a CompactFlash card in order to facilitate identification of the remaining CF-related GPIOs.